We begin this hour with the story of a powerful new genetic test. It can search for genetic mutations linked to about 450 childhood diseases. Severe genetic illnesses in children are rare, but they account for about a fifth of all infant deaths in the U.S. This week, scientists announced the new test, which would be inexpensive and they hope, available to all would-be parents. In a few minutes we'll address some ethical questions this raises.

But, first, Nell Greenfieldboyce reports on this test and the family that inspired it.

NELL GREENFIELDBOYCE: Craig Benson says that a few years ago, he and his wife, Charlotte, noticed a change in their daughter, who was then five years old. Christiane was holding books closer to her face and was sitting closer to the TV.

Mr. CRAIG BENSON: Charlotte and I thought that, well, you know, she needs glasses. So we set up an appointment with an optometrist.

GREENFIELDBOYCE: That first appointment eventually led to a terrible diagnosis: Batten disease.

Mr. BENSON: Batten disease is a very rare genetic neurodegenerative disorder that's caused by both her mom and I carry a gene mutation, a single gene mutation.

GREENFIELDBOYCE: They hadn't known that, of course. They'd never even heard of Batten disease. It's progressive and fatal. A child develops vision loss, seizures, memory problems.

Mr. BENSON: And the last few years are, you know, for the most part, you know, there's really no function to speak of at all. It's, you know, a difficult thing, obviously, to watch any child experience.

GREENFIELDBOYCE: Now, in addition to being a father, Craig Benson is an executive with a biotechnology company in Austin, Texas. Soon after his daughter was diagnosed, he and his colleagues were discussing the fact that one devastating childhood disease, Tay-Sachs, has been virtually eliminated in people with Eastern European Jewish ancestry. This has been done by offering screening tests to would-be parents. If both parents carry the Tay-Sachs mutation, they can take steps so that they won't have a baby with this disease.

Mr. BENSON: Man, we thought, you know, that's a great idea and a great strategy, why is that not more broadly applied?

GREENFIELDBOYCE: So the executives went to Stephen�Kingsmore. He's a researcher who was then at a nonprofit called the National Center for Genome Resources in Santa Fe, New Mexico. They asked him, would it be possible for you to make an affordable test that could screen all prospective parents for numerous genetic diseases? He said yes.

And this week, in the journal Science Translational Medicine, Kingsmore's team describes that test. For less than $400, it can check a person's DNA for all mutations in genes related to nearly 450 severe childhood diseases. And Kingsmore says that's just the beginning.

Mr. STEPHEN KINGSMORE (President, National Center for Genome Resources): Over the next six months we'll be taking the number up to 580 conditions, at which point we'll have represented just about every childhood disease that's severe enough to merit inclusion.

GREENFIELDBOYCE: He says this test is relevant to everyone thinking of having a child, because their research shows it's common for people to carry mutations.

Mr. KINGSMORE: On average, we find that each of us carries two or three mutations that could cause one of these severe childhood diseases.

GREENFIELDBOYCE: If, that is, we were unlucky enough to be having a baby with someone who just happened to be carrying a mutation for that same rare disease.

Laird Jackson thinks this new test raises important issues. He's an expert in prenatal genetic testing at Drexel University.

Professor LAIRD JACKSON (Obstetrics and Gynecology, Drexel University): It's saying that everybody has something to think about here and if testing becomes available, will have something to decide about.

GREENFIELDBOYCE: This new test could become widely available soon. Benson wants to offer it through a nonprofit he started, the Beyond Batten Disease Foundation, so that doctors could offer screening to everyone.

Mr. BENSON: Yeah, I don't know that we've really sat down and contemplated all of the impact that this test and this idea, you know, might have.

GREENFIELDBOYCE: He just hopes it means other families won't have his family's experience - getting blindsinded by a devastating disease that they'd never even heard of.

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